In 1970 David accepted an invitation to join NASA as Chief of its Geophysics and Physics Branch at the Johnson Spacecraft Center, Houston, Texas, and held the position for the next three years. He was responsible for geophysical aspects of the Apollo moon missions, including experiment selection and attendant astronaut training, site selection and real-time mission support. He designed an electromagnetic sounding experiment that astronauts performed successfully while on the surface of the moon. David in 1973 served as interim head of the Lunar and Planetary Institute, Houston, before returning to the University of Toronto. He organized a number of lunar geophysics conferences.